The so-called “Platinum Metals” that constitute the heavier six of the nine Group VIII elements include platinum, ruthenium, osmium, rhodium, iridium and palladium. Although platinum and palladium are especially known for their reflectance and relative stability toward oxidation, each member of this group of elements is separately useful as a catalyst for chemical reactions, particularly oxidation-reduction reactions.
Illustratively, in many applications such as heterogeneous catalysts and fuel cell electrodes, small particles of platinum (Pt) are mounted, by numerous techniques, onto high surface area carbon “supports” or “substrates”. There are myriad companies working toward the development of fuel cell components, and particularly fuel cell electrodes. A commonly cited electrode producer is E-TEK Corporation. Large catalyst manufacturers such as Engelhard and Johnson Matthey are also developing fuel cell components, and numerous smaller ones. Carbon supported Pt and palladium (Pd) catalysts are used extensively in the chemical process industry for hydrogenation reactions, and many other specialty applications. There is also much interest in Pt/carbon electrodes and catalysts in academia.
Because of its expense, it is usually desired to have Pt in the form of very small particles, which maximizes the amount of exposed Pt surface to increase catalytic activity. This condition is known as high “dispersion.” Fuel cell applications require the use of high weight loadings of Pt at high dispersion. Present techniques have the ability to cause the deposit of large amounts of Pt onto high surface area carbon supports, but are cumbersome to use. Similar results are obtained using the other members of the platinum family of elements.
It would therefore be beneficial if a simple method could be found that permits preparation of high weight loadings of members of the platinum metal family of elements at high dispersion on to a high surface area carbon support. The disclosure that follows provides one such method.